1. Field of the Art
Embodiments of the present invention generally relate to the manufacturing of plastics, particularly vapor deposition polymerization of parylene onto a porous material with heat to grow roots of parylene within the pores.
2. Description of the Related Art
Parylene is a generic name for members of a series of poly(p-xylylene) polymers. Parylene polymer is known to excel as a dielectric and as a water vapor barrier without being toxic. Having been commercialized in the 1960s, parylene has found widespread use in the electronics, automotive, aerospace, medical, and other industries. It generally has preferable chemical vapor depositing attributes compared to other conformal coating materials such as acrylics, epoxies, polyurethanes, and silicones. For example, some parylenes can be deposited in extremely thin layers that are relatively strong and essentially pinhole-free. It is precisely these depositing characteristics that make parylene useful in micro/nanofabrication.
Parylene N is the basic member of the series. It is commonly derived from [2.2]paracyclophane, which can be synthesized from p-xylene. Parylene N is typically a completely linear, highly crystalline material.
Parylene C, which has one chlorine group per repeat unit, is another of the series. It is typically produced from the same dimer as parylene N but having a chlorine atom substituted for one of the aromatic hydrogen atoms. Its ease of use and especially well-mannered chemical vapor deposition characteristics make it ideal for use as a conformal coating on printed circuit boards and as a structure or sacrificial intermediate in nanofabricated devices. Its demonstrated bio-compatibility as a United States Pharmacopeial Convention (USP) Class VI biocompatible polymer makes it suitable for medical devices.
Parylene D, which has two chlorine groups per repeat unit, is another common parylene of the series. Although it has better diffusion characteristics than parylene C, parylene D generally deposits less uniformly than parylene C.
Parylene AF-4, with the alpha hydrogen atoms of the N dimer replaced with fluorine, is another parylene of the series. Parylene AF-4 is also known as Parylene SF when manufactured by Kisco Conformal Coating, LLC of California (a subsidiary of Kisco Ltd. of Japan) or PARYLENE HT® when manufactured by Specialty Coating Systems, Inc. of Indianapolis, Indiana.
Other parylenes, such as parylene VT-4, parylene A, parylene AM, and parylene X, are known in the art and are used for specialized products in industry.
Fundamental aspects of parylene N and parylene C are detailed in P. Kramer et al., “Polymerization of Para-Xylylene Derivatives (Parylene Polymerization). I. Deposition Kinetics for Parylene N and Parylene C,” Journal of Polymer Science: Polymer Chemistry Edition, Vol. 22 (1984), pp. 475-491. This journal article is hereby incorporated by reference in its entirety for all purposes.
Fundamental aspects of parylene X are detailed in J. Senkevich et al., “Thermomechanical Properties of Parylene X, A Room-Temperature Chemical Vapor Depositable Crosslinkable Polymer,” Chem. Vap. Deposition, 2007, 13, pp. 55-59. This journal article is hereby incorporated by reference in its entirety for all purposes.
Parylene does not adhere well to some materials, such as polydimethylsiloxane (PDMS). PDMS is a silicone that is widely used for bio-devices, bio-chips, and implants because of its biocompatibility. PDMS is porous, often containing nanometer-scale channels through which liquid water and other body fluids can pass. One type of PDMS is Sylgard 184, manufactured by Dow Corning Corporation, Midland, Mich., U.S.A.
There is a need in the art for better design flexibility in combining biocompatible materials for prosthetics and other devices.